The present invention relates to a pick-up and placement apparatus, and more particularly to a structure of a preferable transfer mechanism for picking up precious components, etc., and moving the same to other places.
Generally speaking, a pick-up and placement apparatus is used for picking up workpieces at a certain place, transferring the same and placing the same at places distant therefrom, and is used to feed various types of components to places where processing and machining are carried out, and remove the same from the processing and machining places. A pick-up and placement apparatus is generally composed of an arm provided with a grasping mechanism, etc., to grasp workpieces and a drive mechanism for reciprocating the arm. The arm is usually driven and reciprocated along an inverted U-shaped motion locus by the drive mechanism. Therefore, the drive mechanism is provided with a drive source such as a drive motor, etc., which actuates the arm portion, and a motion converting portion which transmits power from the drive source to the arm and simultaneously provides the arm with a desired motion.
Apparatuses described in Japanese Patent Publication No. 57240 of 1982 and Japanese Utility Model Publication No. 126522 of 1991 have been brought about as a pick-up and placement apparatus having this type of structure. The abovementioned motion converting portion described in these publications is provided with, for example, a swiveling member which can normally and reversely be turned by a drive motor, a driven member (cam follower) slidably attached to the tip end of the swiveling member in the radial direction, an inverted U-shaped cam groove which guides the corresponding driven member, and a transmitting member such as a transmission lever, gear, etc., which is connected between the driven member and the abovementioned arm as necessary. When the swiveling member swivels, the driven member slides and reciprocates along the cam groove, and the arm is operated in response to a sliding locus of the driven member.
However, in the prior art pick-up and placement apparatus, in order to achieve the abovementioned motions of the arm, the driven member attached to the swiveling member is devised so as to be guided by, for example, an inverted U-shaped cam groove. Therefore, large and excessive loads are given to the drive source due to the sliding resistance and vibration of the swiveling member, driven member and cam groove, and there is a problem when an attempt is made to accelerate the reciprocation speed of the arm.
In particular, since a general cam is composed of, for example, a horizontal portion linearly extending in the left and right direction, an elevating portion linearly extending in the vertical direction, which is disposed at both sides of the moving extent, and a curved portion having a small curvature radius and arcuately extending between the horizontal portion and the elevating portion, a large stress is applied from the cam groove to the swiveling member and driven member at the curved portion provided with a small curvature radius, and thereby causes such a problem that a load applied to the drive source and a drive loss are increased. The drive load and the degree of drive loss are remarkably increased in proportion to a square or a cube of the moving speed of the driven member, which increases in line with an increase in the arm speed.
Also, since the arm is moved in compliance with the driven member that reciprocates along the cam groove as described above, it is necessary to change the shape of the cam groove in order to alter the motion locus of the arm. Therefore, there is another problem in that it is difficult to change the motion locus of the arm.
It is therefore an object of the invention to provide a pick-up and placement apparatus equipped with a novel structure, in which stress is hardly generated when the apparatus operates, and loads applied to the drive source thereof can be reduced.
Further, it is another object of the invention to provide a pick-up and placement apparatus which can increase the speed of motion in the arm.
It is still another object of the invention to provide a pick-up placement apparatus in which the motion locus of the arm portion can be easily changed.
A pick-up and placement apparatus according to the invention has an arm that executes pick-up and placement motions and a drive mechanism that drives the corresponding arm. The corresponding drive mechanism comprises a rotating member that is normally or reversely driven and rotated in an appointed range of rotation, for example by a drive source, a swiveling member that is slidably attached to the corresponding rotating member in the radial direction and normally or reversely swivels in an appointed range of rotation by normal and reverse rotations of the corresponding rotating member, and is provided with a connection portion directly or indirectly linked with the corresponding arm, a retaining means that applies a retaining force to retain the corresponding swiveling member at an appointed position in the radial direction with respect to the corresponding rotating member while slidably retaining the corresponding swiveling member, and a means for regulating and guiding the corresponding connection portion to linearly move the same by directly or indirectly regulating the corresponding swiveling member in the vicinity of both ends in the corresponding range of rotation. The corresponding connection portion is constructed so as to reciprocate on a motion locus consisting of an arcuate locus portion, which is composed by the swiveling of the corresponding swiveling member without being substantially regulated, and a linear locus portion connected to both ends of the corresponding arcuate locus portion and composed by being regulated by the corresponding regulating and guiding means. The corresponding arm carries out motions substantially corresponding to the motion locus of the connection portion.
Since the swiveling member slidably attached to the rotating member swivels while it is retained by the retaining means at an appointed position in the radial direction in a state where it is not substantially regulated, the connection portion moves in a circular arc (that is, along the arcuate locus portion), and when the swiveling member is regulated by the regulating and guiding means in the vicinity of both ends of the range of rotation, the connection portion linearly moves (that is, along the linear locus portion). Resultantly, since the connection portion will reciprocate along an inverted U-shaped locus of movement, the arm will also reciprocate like an inverted U-shape. Therefore, the swiveling member is not substantially regulated other than being restricted by the regulating and guiding means in the vicinity of both ends of the range of rotation, and can freely swivel while maintaining a swiveling radius by the retaining means, wherein there is no case where the swiveling member is always regulated by a cam groove, etc., as in the prior arts. Therefore, the drive load and vibration resulting from regulation of the locus can be reduced. Resultantly, it becomes possible to operate the arm at a high speed. Further, since the locus of movement of the connection portion is composed by connecting the arcuate locus portion and linear locus portion to each other, the connection angle at the corresponding portion can be slackened, and it is possible to suppress or prevent the swiveling member from receiving an impact or generating vibration at the regulation commencing position by the regulating and guiding means. Further, there is no need to constitute an integrated regulating and guide member like a cam groove, and the inverted U-shaped motion locus of the arm are enabled by only providing a regulating and guiding means at both ends of the range of rotation. Therefore, it is possible to simply change the motions of the arm in a wider range by only changing the regulating and guiding position by the regulating and guiding means.
In the abovementioned invention, it is preferable that the retaining means is constructed so as to maintain the abovementioned swiveling member in an appointed position of the maximum swiveling radius in a state where the abovementioned swiveling member does not receive any other regulation, and the regulating and guiding means regulates the swiveling member from the outside of the locus of movement and so as to partially reduce the swiveling radius.
In the invention, it is preferable that, in a state where the abovementioned swiveling member does not receive any regulation, the retaining means is constructed so as to maintain the swiveling member in an appointed position of the minimum swiveling radius, and the regulating and guiding means regulates the swiveling member from the inside of the locus of movement and is constructed so as to partially increase the swiveling radius.
In addition, in the invention, it is preferable that, in a state where the swiveling member does not receive any regulation, the retaining means is constructed so as to maintain the swiveling member at an intermediate position of the slidable range, and the regulating and guiding means regulates the swiveling member from the inside of the locus of movement at a part of the linear locus portions to increase the swiveling radius, and regulates the swiveling member from the outside of the locus of movement in other part of the linear locus portions to reduce the swiveling radius.
In the invention, it is preferable that the retaining means include a resilient member that maintains the position of the swiveling member in the radial direction by a resilient force.
In the invention, it is preferable that the retaining means is provided with a limiting means for determining the limit position of the swiveling member at one side, and a pressing means for pressing the swiveling member toward the abovementioned side. As the limiting means, there is a means having an engagement structure which is engaged at an appointed position in order to regulate a sliding motion of the swiveling member. Also, the pressing member presses the swiveling member to the limiting position which is regulated by the limiting means. For example, there is a resilient member such as a coil spring, etc., or a compression device such as an air cylinder, etc. As a detailed example in this case, a mechanism can be considered, in which the limiting means is constructed so as to limit the maximum swiveling radius of the swiveling means, and the pressing means presses the swiveling member toward the side of the radial direction with respect to the rotating member. In this mechanism, if a resilient member such as a coil spring is used as the pressing means, it is preferable that such a structure is employed in which a compressed resilient member is accommodated between the rotating member and swiveling member, and the limiting means directly or indirectly (for example, via a limiting member) engages the rotating member with the swiveling member, wherein the sliding of the swiveling member is prohibited such that the swiveling radius does not further increase in the engaged state.
In addition, it is preferable that the respective inventions are constructed so as to have a driven member rotatably connected to the connection portion of the swiveling member, for example, a roller (a guide roller 17, etc., described later) and a ring member (for example, an engagement ring 25, etc., described later), and the corresponding driven member is engaged (followed) with the regulating and guiding means to regulate the swiveling member.
Also, in the invention, it is preferable that the swiveling member is rotatably connected to the arm at the connection portion and is provided with a guide supporting means comprising a first guide member to slidably guide the arm in the extending direction of a pair of the linear locus portions connected to both ends of the arcuate locus portion, and a second guide member to guide the abovementioned first guide member movably constructed in the direction of a line that connects one of the linear locus portions with the other of the linear portions. In this case, it is preferable that the regulating and guiding means is constructed so that the swiveling member can move along the locus of movement by regulating the first guide member or the arm.
Further, the invention is provided with a guiding and supporting means, which guides and supports the arm so that it always extends in the same direction from the connection portion, wherein the regulating and guiding means regulates the arm or the guiding and supporting means, and then the connection portion is moved along the locus of movement by the regulation.
Also, although the respective inventions are constructed so that the extending direction at the linear locus portion of the locus of movement has an angle less than 90 degrees with respect to the tangential direction at the end portion of the arcuate locus portion, it is preferable that the angle is between 0 and 40 degrees, and in particular it is preferable that the angle is between 0 and 30 degrees. Especially, it is most preferable that the angle is almost zero, that is, the linear locus portion extends in roughly a direction tangential to the end position of the abovementioned arcuate locus portion. If so, it is possible to decrease the impact and load stress fluctuation that the swiveling member receives when regulation is commenced by the regulating and guiding means.
Further, in the respective inventions, it is preferable that the linear locus portion of the locus of movement is set to be parallel to the tangential line at one point on an extended circular arc of the arcuate locus portion and has an equal locus length at both sides of the point. That is, the abovementioned linear locus portion is formed at one point in parallel to the tangential line and is constructed so that the straight line extending from the above point to the center of swivel becomes perpendicular bisector of the linear locus portion. If so, since the amount of fluctuation in the swiveling radius of the swiveling member due to regulation of the regulating and guide member can be reduced and it is possible to secure a sufficient length of the linear locus portion, the drive load can be decreased, and at the same time noise and vibration can be lowered.
Still further, in the respective inventions, a means having a regulating and guiding plane by which the swivel member is regulated in the direction that increases a swiveling radius, a means having a regulating and guiding plane by which the swivel member is regulated in the direction of decreasing a swiveling radius, and a means having a pair of regulating and guiding planes by which the swivel member is regulated in both the increasing and decreasing directions may be listed as the abovementioned regulating and guiding means. In this case, such a structure, which has a pair of regulating and guiding planes by which the swiveling member is regulated in both the directions of increasing and decreasing an swiveling radius, can be constructed by a groove-shaped member.
In the respective invention, it is preferable that the respective regulating and guiding planes are made flat.